The present invention relates to a control system and method for vibration welding thermoplastics.
Vibration welding is achieved by vibrating two parts under pressure along their common interface to generate frictional heat to melt and fuse thermoplastic parts together. Vibration welding is a fast inexpensive way to join irregularly shaped parts that are large or small.
Presently, vibration welding is used in non-demanding (i.e. limited load-bearing) applications. However, in application such as plastic bumpers for automobiles, where the welds have to withstand high impact, not enough has been known on how to achieve repeatability and adequate weld strengths.
Vibration weld parameters are set by trial and error. Once a pressure and frequency have been selected, each weld is accomplished by performing the vibration for a predetermined time that is found to be satisfactory. The time parameter when used as the variable for terminating the weld process is sensitive to part uniformity and slight variations in pressure. Minor variations in part geometry can result in significant changes in the weld time required for a quality weld.
It is an object of the present invention to provide a method and a control system for a weld machine that provides uniform quality welds that are repeatable.